Antimicrobial activities of Eugenol and Cinnamaldehyde against the human gastric pathogen Helicobacter pylori

Antibacterial effect of plant-derived antimicrobials on major bacterial mastitis pathogens in vitro

The objective of this study was to investigate the antimicrobial effect of plant-derived antimicrobials including trans-cinnamaldehyde (TC), eugenol, carvacrol, and thymol on major bacterial mastitis pathogens in milk. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the aforementioned compounds on Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Staphylococcus aureus, and Escherichia coli were determined. In addition, the bactericidal kinetics of TC on the aforementioned pathogens and the persistence of the antimicrobial activity of TC in milk over a period of 2 wk were investigated. All 4 plant-derived molecules exhibited antimicrobial activity against the 5 mastitis pathogens tested, but TC was most effective in killing the bacteria. The MIC and MBC of TC on Staph. aureus, E. coli, and Strep. uberis were 0.1 and 0.45%, respectively, whereas that on Strep. agalactiae and Strep. dysgalactiae were 0.05 and 0.4%, respectively. The MIC and MBC of the other 3 molecules ranged from 0.4 to 0.8% and 0.8 to 1.5%, respectively. In time-kill assays, TC at the MBC reduced the bacterial pathogens in milk by 4.0 to 5.0 log(10) cfu/mL and to undetectable levels within 12 and 24 h, respectively. The antimicrobial effect of TC persisted for the duration of the experiment (14 d) without any loss of activity. Results of this study suggest that TC has the potential to be evaluated as an alternative or adjunct to antibiotics as intramammary infusion to treat bovine mastitis.

Shelf life of semifried tuna slices coated with essential oil compounds after treatment with anodic electrolyzed NaCl solution

The main objective of this study was to evaluate the effect of two commonly used essential oils after treatment with anodic electrolyzed NaCl solution in order to extend the shelf life of coated semifried tuna slices. Samples of tuna slices were treated with 100-fold electrolyzed water and coated with an edible solution containing 1% essential oil (0.5% eugenol [E] plus 0.5% linalool [L]). The coated slices were fried at 170 degrees C for 1 min and then stored at 5 and 25 degrees C. Total volatile basic nitrogen of slices treated with electrolyzed water and 1% (E+L) decreased from 15.5 for the nontreated control slices to 9.7 immediately after treatment and remained at a low level (<30) until the end of the storage period (day 20). Treatment with 1% (E+L) significantly suppressed lipid oxidation in coated semifried tuna. Sensory evaluation and microbiological assays showed that treatment with electrolyzed water and 1% (E+L) extended the shelf life of coated semifried slices to 15 and 2 days compared with 5 and 1 days for control slices during storage at 5 and 25 degrees C, respectively.

Inhibition of Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii by plant oil aromatics

The inhibitory effect of some plant oil aromatics against three strains of Arcobacter butzleri, two strains of Arcobacter cryaerophilus, and one strain of Arcobacter skirrowii was evaluated. When MICs were determined using the broth macrodilution method, cinnamaldehyde was most inhibitory followed by thymol, carvacrol, caffeic acid, tannic acid, and eugenol (P < 0.001). Sublethal concentrations of the three most potent plant oil aromatics also were examined. Overall, cinnamaldehyde was the most bacteriostatic against all arcobacters tested except A. butzleri when these strains were exposed to the MIC25 of this aromatic aldehyde. The bacteriostatic activities of thymol and carvacrol were concentration and species dependent.

Inhibition of bacterial cell division protein FtsZ by cinnamaldehyde

Cinnamaldehyde is a natural product from spices that inhibits cell separation in Bacillus cereus. Cell division is regulated by FtsZ, a prokaryotic homolog of tubulin. FtsZ assembles into the Z-ring at the site of cell division. Here, we report the effect of cinnamaldehyde on FtsZ and hence on the cell division apparatus. Cinnamaldehyde decreases the in vitro assembly reaction and bundling of FtsZ. It is found that cinnamaldehyde perturbs the Z-ring morphology in vivo and reduces the frequency of the Z ring per unit cell length of Escherichia coli. In addition, GTP dependent FtsZ polymerization is inhibited by cinnamaldehyde. Cinnamaldehyde inhibits the rate of GTP hydrolysis and binds FtsZ with an affinity constant of 1.0+/-0.2 microM(-1). Isothermal titration calorimetry reveals that binding of cinnamaldehyde to FtsZ is driven by favorable enthalpic interactions. Further, we map the cinnamaldehyde binding region of FtsZ, using the saturation transfer difference-nuclear magnetic resonance and an in silico docking model. Both predict the cinnamaldehyde binding pocket at the C terminal region involving the T7 loop of FtsZ. Our results show that cinnamaldehyde binds FtsZ, perturbs the cytokinetic Z-ring formation and inhibits its assembly dynamics. This suggests that cinnamaldehyde, a small molecule of plant origin, is a potential lead compound that can be developed as an anti-FtsZ agent towards drug design.

In vitro antibacterial activity of some plant essential oils

BACKGROUND

To evaluate the antibacterial activity of 21 plant essential oils against six bacterial species.

METHODS

The selected essential oils were screened against four gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris) and two gram-positive bacteria Bacillus subtilis and Staphylococcus aureus at four different concentrations (1:1, 1:5, 1:10 and 1:20) using disc diffusion method. The MIC of the active essential oils were tested using two fold agar dilution method at concentrations ranging from 0.2 to 25.6 mg/ml.

RESULTS

Out of 21 essential oils tested, 19 oils showed antibacterial activity against one or more strains. Cinnamon, clove, geranium, lemon, lime, orange and rosemary oils exhibited significant inhibitory effect. Cinnamon oil showed promising inhibitory activity even at low concentration, whereas aniseed, eucalyptus and camphor oils were least active against the tested bacteria. In general, B. subtilis was the most susceptible. On the other hand, K. pneumoniae exhibited low degree of sensitivity.

CONCLUSION

Majority of the oils showed antibacterial activity against the tested strains. However Cinnamon, clove and lime oils were found to be inhibiting both gram-positive and gram-negative bacteria. Cinnamon oil can be a good source of antibacterial agents.

Antimicrobial activity of Sapindus mukorossi and Rheum emodi extracts against H pylori: In vitro and in vivo studies

AIM: To evaluate the antibacterial activity of Sapindus mukorossi (S. mukorossi) and Rheum emodi (R. emodi).

METHODS: Powders of S. mukorossi and R. emodi were extracted successively with petroleum ether, benzene, chloroform and ethanol and were concentrated in vacuum. The disk diffusion method was used for in vitro studies and in vivo studies were performed on male Wister rats. Thirty resistant clinical isolates of H pylori, as determined by their antibiotic sensitivity patterns by E-test, along with two Gram +ve (S. aureus, B. subtilis) and two Gram -ve (E. coli, P. vugaris) organisms were screened for their susceptibility patterns against these extracts.

RESULTS: In our screening, all 30 resistant isolates and the other four organisms (two Gram +ve S. aureus, B. subtilis and two Gram -ve, E. coli, P. vugaris) were sensitive to the test compounds. It was found that ethanol and chloroform extracts of S. mukorossi and ethanol and benzene extracts of R. emodi inhibited H pylori at very low concentrations. In the in vitro study, the isolates showed a considerable zone of inhibition at very low concentrations (10 μg/mL) for both the extracts. In the in vivo study, the H pylori infection was cleared with minimal doses of extracts of S. mukorossi (2.5 mg/mL) and R. emodi (3.0 mg/mL) given orally for seven days.

CONCLUSION: We can conclude from this study that the extracts of S. mukorossi and R. emodi inhibited the growth of pylori in vitro and, in in vivo studies, the H pylori infection cleared within seven days at very low concentrations. We also found that H pylori did not acquire resistance against these herbal extracts even after 10 consecutive passages.

Essential oils--their antimicrobial activity against Escherichia coli and effect on intestinal cell viability

Essential oils are known to possess antimicrobial activity against a wide spectrum of bacteria. The main objective of this study was to evaluate possible harmful effects of four commonly used essential oils and their major components on intestinal cells. Antimicrobial activity of selected plant extracts against enteroinvasive Escherichia coli was dose dependent. However, doses of essential oils with the ability to completely inhibit bacterial growth (0.05%) showed also relatively high cytotoxicity to intestinal-like cells cultured in vitro. Lower doses of essential oils (0.01%) had only partial antimicrobial activity and their damaging effect on Caco-2 cells was only modest. Cell death assessment based on morphological and viability staining followed by fluorescence microscopy showed that essential oils of cinnamon and clove and their major component eugenol had almost no cytotoxic effect at lower doses. Although essential oil of oregano and its component carvacrol slightly increased the incidence of apoptotic cell death, they showed extensive antimicrobial activity even at lower concentrations. Relatively high cytotoxicity was demonstrated by thyme oil, which increased both apoptotic and necrotic cell death incidence. In contrast, its component thymol showed no cytotoxic effect as well as greatly-reduced ability to inhibit visible growth of the chosen pathogen in the doses used. On the other hand, the addition of all essential oils and their components at lower doses, with the exception of thyme oil, to bacterial suspension significantly reduced the cytotoxic effect of E. coli on Caco-2 cells after 1h culture. In conclusion, it is possible to find appropriate doses of essential oils showing both antimicrobial activity and very low detrimental effect on intestinal cells.